I have found that the best source for Indian tea is none other than one's local Indian grocer. Nevermind Twinings or Taylors of Harrogate, whose teas are lovely, of course, but pricey. One is never sure from the "brand name" teas, anyway, of obtaining an authentic tea; 80% of all so-called Darjeelings sold in the world are not actually from the Darjeeling region, whereas one can find in Indian grocers packages sporting the official Tea Board logos indicating the authenticity of the Assam, Darjeeling, or Nilgiri tea one purchases--and bought for a pittance!
This is why I was crestfallen when I discovered, after having moved into our small midwestern town, that there wasn't a single Indian grocer within a 50-mile radius. Forced to resort to online ordering, I was delighted to chance upon a tea shop selling superb high-grade bulk teas at wonderful prices. And so out with the credit card to punch in a few letters and numbers that will bring to my doorstep massive quantities of Assam, Ceylon, and East Friesian teas to be warmly and heartily consumed on cold, midwestern mornings. All is right with the world again.